Which property allows you to write the expression (3+7i)+(8-6i) as (8-6i)+(3+7i) square Which property allows you to write the expression [(3+7i)+(8-6i)]+(1+9i) as (3+7i)+[(8-6i)+(1+9i)] square commutative associative distributive

The property that allows you to write the expression $$(3+7i)+(8-6i)$$ as $$(8-6i)+(3+7i)$$ is the commutative property of addition. The commutative property states that the order in which numbers are added does not affect the sum.

The property that allows you to write the expression $$[(3+7i)+(8-6i)]+(1+9i)$$ as $$(3+7i)+[(8-6i)+(1+9i)]$$ is the associative property of addition. The associative property states that the way in which numbers are grouped when being added does not affect the sum.

Therefore, the correct answer is:
associative